DE112004003061B4 - Use of a positive resist composition - Google Patents

Abstract

The use of a positive resist composition for forming a resist pattern by a method comprising an immersion lithography step, wherein when X1 denotes sensitivity, when a 1: 1 line-and-space resist pattern of 130 nm is formed in a normal exposure lithography method using a light source having a wavelength of 193 nm, and X2 denotes the sensitivity when obtaining an identical 1: 1 line-and-space resist pattern of 130 nm by a simulated immersion lithography method in which a step of bringing a solvent for said immersion lithography into contact between the step of selective irradiation and a step of baking after irradiation of a normal exposure lithography method using a light source having a wavelength of 193 nm is as stated Positive resist composition is a positive resist composition, i ie, as the resin component, a silsesquioxane resin for which an absolute value of [(X 2 / X 1) - 1] × 100 is not more than 8.0.

Description

Technical area

The present invention relates to the use of a positive resist composition in a method of forming a resist pattern including an immersion lithography step

State of the art

In the production of semiconductor elements and liquid crystal display elements, a lithography step in which a circuit pattern (resist pattern) is formed in a resist provided on the surface of a substrate and an etching step in which the formed resist pattern as a mask is used to partially etch and remove an insulating film or a conductive film formed as a base material on the surface of the substrate.

In recent years, advances in lithography techniques have led to a continuing rapid miniaturization of resist patterns. Recently, levels for resolution capable of forming line and space patterns of not more than 100 nm and isolated patterns of not more than 70 nm have been demanded.

A typical technique for achieving miniaturization involves shortening the wavelength of the light source used for the irradiation. While conventional ultraviolet radiation such. For example, g-lines and i-lines have been used as the light source for the irradiation, in particular, mass production using KrF excimer lasers (248 nm) has already started today, and even with the introduction of ArF excimer lasers (193 nm) started. Furthermore, the use of even shorter wavelengths such. B. F ₂ -Excimerlasern (157 nm), EUV (extreme ultraviolet), electron beams, X-rays and soft X-rays are investigated.

An example of a known resist material that meets the high resolution requirements required to allow the reproduction of a pattern of very small dimensions is a so-called positive chemically amplified resist composition containing a base resin. which has an increased solubility in alkali under the action of acid, and an acid generator which generates acid upon irradiation dissolved in an organic solvent. Recently, chemically amplified resist compositions suitable for irradiation with short wavelength light sources of not more than 200 nm have also been proposed (for example, see Patent Document 1).

However, although chemically amplified resists exhibit high sensitivity and high resolution, they are not ideal for the formation of a single aspect, high aspect ratio resist pattern which is required to ensure favorable resistance to dry etching. If an attempt is made to form a resist pattern with an aspect ratio of 4 to 5, the collapse of the pattern may become problematic.

On the other hand, as a method which enables the formation of a resist pattern having a high resolution and a high aspect ratio (see, for example, Patent Documents 2 and 3), a two-layer resist method comprising a chemically amplified resist has been proposed used. In this method, an organic film is first formed on the surface of a substrate as the lower resist layer. An upper resist layer is then formed on the surface of the lower resist layer by using a chemically amplified resist containing a specific silicon-containing polymer. Subsequently, a resist pattern is formed in the upper resist layer using photolithography techniques. Then, when this resist pattern is used as a mask for performing the etching, thereby transferring the resist pattern to the lower resist layer, a resist pattern having a high aspect ratio is formed.

• [Patentdokument 1] JP 2002-162 745 A
• [Patentdokument 2] JP H06-202 338 A
• [Patentdokument 3] JP H08-29 987 A

In addition, although the development of a silicon-containing resist composition which can be ideally applied to a method of forming a resist pattern containing an immersion lithography step as disclosed in Non-Patent Documents 1 to 3 is intensively sought but no publications relating to such composition have been published so far.

• [Patent Document 1] JP 2002-162 745 A
• [Patent Document 2] JP H06-202 338 A
• [Patent Document 3] JP H08-29 987 A

• [Non-Patent Document 1] Journal of Vacuum Science & Technology B (U.S.), 1999, 17, No. 6, pp. 3306-3309.
• [Non-Patent Document 2] Journal of Vacuum Science & Technology B (U.S.), 2001, 19, No. 6, pp. 2353-2356.
• [Non-Patent Document 3] Proceedings of SPIE (U.S.), 2002, 4691, pages 459-465

The chemically amplified resists used in the type of the two-layer resist methods described above show no particular problems when used in light sources having comparatively long wavelengths, e.g. B. irradiation with i-lines. However, when a comparatively short-wavelength high-energy light having a wavelength of not more than 200 nm (such as an ArF excimer laser or the like) or an electron beam is used as the light source for the irradiation, the absorption is large and the transparency is bad, which means that the formation of a resist pattern with high resolution is difficult. Furthermore, another problem arises in that during the irradiation of the resist, an organic gas is generated (degassing), which can pollute the irradiation apparatus and the like. This organic gas can be broadly classified into two types: silicon-based organic gases generated by the breakage of silicon-carbon bonds within the silicon-containing polymer, and organic non-silicon gases generated during either the cleavage of the acid-cleavable, the dissolution-inhibiting groups or the resist solvent are formed. These two types of gases can cause a deterioration in the transparency of the lenses within the irradiation device. In particular, in the case of the foregoing gas type, if it once adheres to a lens, the subsequent removal is extremely difficult. This can be a significant problem.

The publications JP 2002-268227 A . US 2002/0081520 A1 and US 2002/0012871 A1 describe positive resist compositions comprising as a resin component a silsesquioxane resin.

In the publication SWITKES, M; ROTHSCHILD M .: Resolution Enhancement of 157 nm Lithography by Liquid Immersion. In: Proceedings of SPIE, Vol. 4691, 2002, pages 459-465, the use of immersion lithography in the production of resist patterns is proposed, it being noted that the same or similar resist compositions as in the conventional lithography and in the same wavelength can be used and this requires no development of new light sources, optical materials or coatings. It is also mentioned that immersion lithography can allow to increase the resolution of projection lithography.

The publication HOFFNAGLE, J. A .; HINSBERG, W. D .; SANCHEZ, M .; HOULE F.A .: Liquid immersion deep ultraviolet interferometric lithography. In: J. Vac. Sc. Techno. B. Vol. 17. 1999, no. 6, pages 3306-3309, relates to the use of immersion lithography for the production of a resist pattern using a commercial, conventional resist composition which need not be modified or adapted. It is also mentioned that the wavelength can be reduced so that a higher resolution can be achieved by using immersion lithography.

The publication SWITKES, M .; ROTHSCHILD, M .: immersion lithography at 157 nm. In: J. Vac. Sci. Technol. B, Vol. 19, 2001, no. 6, pages 2353-2356, describes that by using immersion lithography, improved resolution can be achieved and that the implementation of immersion lithography, starting from a conventional lithography, does not require any special adaptation of the conditions or the resist composition used.

Disclosure of the invention

Therefore, it is an object of the present invention to provide a use for a positive resist composition for forming a resist pattern, wherein the positive resist composition comprises provides high levels of transparency and is capable of preventing the above-described degassing phenomenon, and is ideal for use with immersion lithography.

As a result of intensive research, the inventors of the present invention have discovered that the use of a positive resist composition according to independent claim 1 containing a silsesquioxane resin is capable of achieving the objects described above and therefore capable of to complete the present invention.

In other words, a first aspect of the present invention is the use of a resist composition used in a method of forming a resist pattern including an immersion lithography step, wherein when X1 denotes sensitivity, when a 1: 1 Line and space resist pattern of 130 nm is formed by a normal irradiation lithography process using a light source with a wavelength of 193 nm, where X2 is the sensitivity when an identical 1: 1 line-and-space Resist pattern of 130 nm formed by a simulated immersion lithography method in which a step of contacting an immersion lithography solvent with the resist film between the selective irradiation step and the post-irradiation baking step ("Post Exposure Baking" (PEB)) of a normal irradiation lithography process using a light source m used with a wavelength of 193 nm, the resist composition is a positive resist composition containing a silsesquioxane resin as the resin component for which the absolute value of [(X 2 / X 1) -1] x 100 is no longer is 8.0.

• (i) Im Hinblick auf die Leistungsfähigkeit des optischen Systems ist es klar, wenn man sich den Fall vorstellt, bei dem eine photographische lichtempfindliche Platte mit einem vorteilhaften oberflächlichen Wasserwiderstand in Wasser eingetaucht wird und ein gemustertes Licht dann auf die Oberfläche der Platte gestrahlt wird, dass in der Theorie, unter der Voraussetzung, dass kein Verlust an Lichtdurchlässigkeit wie z. B. durch Reflexion oder Ähnliches an der Wasseroberfläche oder der Grenzfläche zwischen dem Wasser und der Oberfläche der lichtempfindlichen Platte auftritt, keine nachfolgenden Probleme entstehen sollten. Der Verlust an Lichtdurchlässigkeit in dieser Situation kann leicht durch Optimierung des Auftreffwinkels des Bestrahlungslichtes behoben werden. Daher wird vermutet, dass unabhängig davon, ob das zu Ziel der Bestrahlung ein Resist-Film, eine photographische lichtempfindliche Platte oder ein abbildender Schirm ist, unter der Voraussetzung, dass das Ziel inaktiv im Hinblick auf das Immersions-Lösungsmittel ist, nämlich, dass es weder durch das Immersions-Lösungsmittel beeinträchtigt wird, noch das Immersions-Lösungsmittel beeinträchtigt, dass es keine Änderung in der Leistungsfähigkeit des optischen Systems gibt. Daher erfordert dieser Faktor keinen neuen Test.
• (ii) Der Effekt des Resist-Filmes auf das Immersions-Lösungsmittel bezieht sich spezifisch auf das Auslaugen von Komponenten aus dem Resist-Film heraus in die Lösung, wodurch der Brechungsindex des Immersions-Lösungsmittels geändert wird. Wenn sich der Brechungsindex des Immersions-Lösungsmittels ändert, dann ist es ausgehend von der Theorie ohne Durchführung weiterer Tests vollkommen klar, dass die optische Auflösung der gemusterten Bestrahlung durch diese Änderung beeinflusst wird. Dieser Faktor kann angemessen dadurch bestimmt werden, dass entweder eine Änderung in der Zusammensetzung des Immersions-Lösungsmittels oder eine Änderung im Brechungsindex des Lösungsmittels als ein Ergebnis des Herauslösens einer Resist-Komponente nach dem Eintauchen des Resist-Filmes in das Immersions-Lösungsmittel bestätigt wird. Es besteht dann keine Notwendigkeit, tatsächlich gemustertes Licht auf den Resist zu strahlen, und dann den Resist zu entwickeln und die Auflösung zu bestimmen. Wenn gemustertes Licht auf den Resist-Film in dem Immersions-Lösungsmittel gestrahlt wird und dann der Resist entwickelt und die Auflösung bestimmt wird, gibt es im Gegensatz hierzu selbst beim Nachweis einer Änderung in der Auflösung keine Möglichkeit zur Unterscheidung, ob die Änderung ein Ergebnis des Abbaus des Immersions-Lösungsmittels, welcher die Auflösung beeinflusst, eines Abbaus im Resist-Film, der die Auflösung beeinflusst, oder eine Kombination von beiden Faktoren ist.
• (iii) Die Zersetzung des Resist-Filmes, die durch das Immersions-Lösungsmittel hervorgerufen wird und zu einer Verschlechterung der Auflösung führt, kann angemessen durch eine einfache Auswertung ermittelt werden, wobei ein Behandlungsschritt, in dem das Immersions-Lösungsmittel mit dem Resist-Film in Kontakt gebracht wird, z. B. durch Sprayen in Form einer Dusche, zwischen den Schritt der selektiven Bestrahlung und den Schritt des Backens nach der Bestrahlung („post exposure baking” (PEB)) eingeschoben wird, und der Resist-Film dann entwickelt und die Auflösung des resultierenden Resist-Musters analysiert wird. Weiterhin stellt bei dieser Methode der Auswertung das Spritzen des Immersions-Lösungsmittels direkt auf den Resist-Film sicher, dass die Eintauchbedingungen strikter sind. Wenn die Bestrahlung durchgeführt wird, während der Resist-Film im vollständig eingetauchten Zustand ist, kann unmöglich bestimmt werden, ob irgendeine Änderung in der Auflösung ein Effekt der Zersetzung des Immersions-Lösungsmittels, ein Ergebnis der Zersetzung der Resist-Zusammensetzung, die durch das Immersions-Lösungsmittel hervorgerufen wird, oder eine Kombination beider Faktoren ist.

In order to evaluate the performance of forming the resist pattern by immersion lithography, it was considered appropriate to analyze three factors: namely, (i) the performance of the optical system using immersion lithography, (ii) the effect of the resist film on the immersion lithography. Solvent and (iii) the degradation of the resist film caused by the immersion solvent.

• (i) In view of the performance of the optical system, it is clear to imagine the case where a photographic photosensitive plate having a favorable water surface resistance is immersed in water and a patterned light is then irradiated to the surface of the plate. that in theory, provided that no loss of light transmission such. By reflection or the like at the water surface or the interface between the water and the surface of the photosensitive plate, no subsequent problems should arise. The loss of light transmission in this situation can be easily remedied by optimizing the angle of incidence of the irradiation light. Therefore, it is presumed that irrespective of whether the target of irradiation is a resist film, a photographic photosensitive plate, or an imaging screen, provided that the target is inactive with respect to the immersion solvent, that is neither is affected by the immersion solvent, nor does it affect the immersion solvent, that there is no change in the performance of the optical system. Therefore, this factor does not require a new test.
• (ii) The effect of the resist film on the immersion solvent specifically refers to the leaching of components from the resist film into the solution, thereby changing the refractive index of the immersion solvent. If the refractive index of the immersion solvent changes, then it is perfectly clear from theory, without further testing, that the optical resolution of the patterned radiation is affected by this change. This factor can be suitably determined by confirming either a change in the composition of the immersion solvent or a change in the refractive index of the solvent as a result of taking out a resist component after immersing the resist film in the immersion solvent. There is then no need to actually project patterned light onto the resist, and then develop the resist and determine the resolution. In contrast, when patterned light is irradiated on the resist film in the immersion solvent and then the resist is developed and the resolution is determined, there is no possibility of discriminating whether the change is a result of the change even in the detection of a change in resolution Degradation of the immersion solvent, which affects the resolution, degradation in the resist film, which affects the resolution, or a combination of both factors.
• (iii) The decomposition of the resist film caused by the immersion solvent and resulting in the deterioration of the resolution can be adequately determined by a simple evaluation, wherein a treatment step in which the immersion solvent with the resist film is brought into contact, for. By spray in the form of a shower, between the step of selective irradiation and the post exposure baking (PEB) step, and then the resist film is developed and the resolution of the resulting resist is applied. Pattern is analyzed. Further, in this evaluation method, spraying the immersion solvent directly onto the resist film ensures that the immersion conditions are more strict. When the irradiation is performed while the resist film is in the fully immersed state, it can not be determined if any change in resolution is an effect of decomposing the immersion solvent, a result of decomposition of the resist composition caused by the immersion Solvent is caused, or a combination of both factors.

The phenomena (ii) and (iii) are inextricably linked and can be identified by confirming deterioration in either the pattern shape or the sensitivity caused by the effect of the immersion solvent on the resist film. Therefore, the study of factor (iii) can only be considered to include the study of factor (ii).

Based on these analyzes, suitability for immersion lithography of a resist film formed from the new resist composition, which was considered to be ideal for immersion lithography methods, was confirmed by a rating test (hereinafter referred to as "evaluation test 1") wherein a treatment step in which an immersion solvent is brought into contact with the resist film, e.g. By spray in the form of a shower, between the step of selective irradiation and the post exposure baking (PEB) step, and the resist film is then developed and the resolution of the resulting resist Pattern is analyzed.

In addition, in another evaluation method, which is a development of the evaluation method 1, additional confirmation was made by a evaluation test representing a simulation of an actual manufacturing process (hereinafter referred to as "evaluation test 2"), wherein the patterned irradiation light is interference light from a prism is replaced and the sample is put in an actual state of immersion and irradiated (a double-beam interference irradiation method).

Best way to carry out the invention

The following is a description of embodiments of the present invention.

<< silsesquioxane resin >>

worin R¹ und R² jeweils unabhängig voneinander eine geradkettige, verzweigte oder cyclische gesättigte aliphatische Kohlenwasserstoffgruppe darstellen,
R³ eine durch Säure abspaltbare, die Auflösung verhindernde Gruppe darstellt, die eine Kohlenwasserstoff-Gruppe umfasst, die eine aliphatische monocyclische oder polycyclische Gruppe enthält,
R⁴ ein Wasserstoffatom oder eine geradkettige, verzweigte oder cyclische Alkylgruppe darstellt,
jede X-Gruppe unabhängig voneinander eine Alkylgruppe mit 1 bis 8 Kohlenstoffatomen darstellt, in der mindestens ein Wasserstoffatom durch ein Fluoratom ersetzt worden ist, und
m eine ganze Zahl von 1 bis 3 darstellt.A silsesquioxane resin which is preferably used in the present invention contains the structural units represented by the general formulas [1] and [2]:

wherein R ¹ and R ² each independently represent a straight-chain, branched or cyclic saturated aliphatic hydrocarbon group,
R ^{3 represents} an acid dissociable, dissolution inhibiting group comprising a hydrocarbon group containing an aliphatic monocyclic or polycyclic group,
R ^{4 represents} a hydrogen atom or a straight-chain, branched or cyclic alkyl group,
each X group independently represents an alkyl group having 1 to 8 carbon atoms in which at least one hydrogen atom has been replaced by a fluorine atom, and
m represents an integer of 1 to 3.

In this specification, the term "structural unit" refers to a monomer unit which contributes to the formation of a polymer.

In the general formulas [1] and [2], R ¹ and R ² may be either the same group or different groups, and each represents a straight-chained, branched or cyclic saturated aliphatic hydrocarbon group in which the number of carbon atoms is from the standpoint of the best Control of the solubility in the resist solvent and the molecular size is preferably from 1 to 20, and more preferably from 5 to 12. Cyclic saturated aliphatic hydrocarbon groups are particularly preferred because they provide the benefits of producing silsesquioxane resins with good transparency to high energy light, high glass transition temperatures (Tg) and better control of acid generator production during PEB.

As these cyclic saturated aliphatic hydrocarbon groups, either monocyclic groups or polycyclic groups can be used. Examples of polycyclic groups include groups in which two hydrogen atoms have been removed from a dicycloalkane, tricycloalkane or tetracycloalkane or the like, and specific examples include groups in which two hydrogens are selected from a polycycloalkane such as polyhydric. As adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane were removed.

More specific examples of R ¹ and R ² include groups in which two hydrogen atoms have been removed from an alicyclic compound selected from a group consisting of the compounds represented by the following formulas [3] to [8]. and derivatives thereof. [Formula 7]

Here, the term "derivative" means an alicyclic compound having one of the formulas [3] to [8], wherein at least one of the hydrogen atoms is represented by a lower alkyl group having 1 to 5 carbon atoms, such as. As a methyl group or ethyl group, an oxygen atom or a halogen atom such as. As fluorine, chlorine or bromine, has been replaced.

Of the above groups, preferred are groups in which two hydrogen atoms have been removed from an alicyclic compound selected from the group consisting of the compounds represented by the formulas [3] to [8] These have a superior transparency and industrially are also very readily available.

R ³ represents an acid dissociable, dissolution inhibiting group formed from a hydrocarbon group containing an aliphatic monocyclic or polycyclic group. This acid dissociable, dissolution inhibiting group has an alkali dissolving effect which renders the entire silsesquioxane resin insoluble in alkali prior to irradiation, but then under the action of acid produced from the acid generator after irradiation , cleaves, making the entire silsesquioxane resin soluble in alkali.

The silsesquioxane resin (A1) preferably used in the present invention contains acid dissociable, dissolution inhibiting groups formed from hydrocarbon groups containing bulky aliphatic monocyclic or polycyclic groups, such as those represented by the formulas [9] to [below] shown below. 13]. As a result, when the silsesquioxane resin is used as a base resin in a positive resist composition, the post-cleavage-preventing groups are much less likely to be converted to gas than conventional acid-cleavable, dissolution-inhibiting groups which are not a cyclic group contain and the straight-chain alkoxyalkyl groups such as. For example, 1-ethoxyethyl, cyclic ether groups such as. As tetrahydropyranyl groups or branched chain-like tertiary alkyl groups such as. B. Tertiärbutyl groups, thereby allowing that the above-mentioned degassing phenomenon is prevented.

From the viewpoint of preventing the gassing of the cleaved groups, while also securing appropriate solubility levels in the resist solvent and the developing solution, the number of carbon atoms within the group R ^{3 is} preferably from 7 to 15, and more preferably from 9 to 13th

Provided that the acid-cleavable dissolution-preventing group is formed of a hydrocarbon group containing an aliphatic monocyclic or polycyclic group, the actual group may be suitably in accordance with the irradiation source among a variety of groups suitable for resist composition resins for use with ArF excimer lasers and the like. Groups which form a tertiary alkyl cyclic ester with the carboxyl group of a (meth) acrylate are particularly well known.

Acid-cleavable, dissolution-inhibiting groups containing an aliphatic polycyclic group are particularly preferred. This aliphatic polycyclic group may be suitably selected from a variety of groups proposed for use in ArF resists. Examples of these aliphatic polycyclic groups include groups in which a hydrogen atom has been removed from a bicycloalkane, tricycloalkane or tetracycloalkane or the like, and specific examples include groups in which a hydrogen atom is selected from a polycycloalkane, e.g. As adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane has been removed.

Particularly preferable examples include any group selected from a group consisting of the following formulas [9] to [13].

[Formula 8]

Silsesquioxane resins containing 2-methyl-2-adamantyl groups represented by the formula [II] and / or 2-methyl-2-adamantyl groups represented by the formula [12] are particularly preferable. Since these are resistant to degassing and also superior resist characteristics such. B. resolution and heat resistance.

R ⁴ represents a hydrogen atom or a straight chain, branched or cyclic alkyl group. From the viewpoint of solubility in the resist solvent, the number of carbon atoms within the alkyl group is preferably from 1 to 10, and lower alkyl groups having from 1 to 4 carbon atoms are particularly desirable.

Specific examples of the alkyl group include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl or n-octyl.

The R ⁴ group is suitably selected in accordance with the desired solubility of the silsesquioxane resin in alkali. The solubility in alkali is greatest when R ^{4 is} a hydrogen atom. Increased solubility in alkali offers the advantage of increased sensitivity.

In contrast, the alkali solubility of the silsesquioxane resin decreases as the number of carbon atoms within the alkyl group increases or as the bulkiness of the group increases. When the solubility in alkali decreases, the resistance to an alkali developing solution increases, whereby an improvement in the bandwidth for irradiation is achieved when the silsesquioxane resin is used for the formation of a resist pattern, and the extent of the dimensional variation accompanying the irradiation is reduced. Furthermore, developing irregularities are also reduced, which means that the roughness within the edge portions of the formed resist pattern can also be improved.

X represents a straight-chain, branched or cyclic alkyl group, although it is preferably a straight-chain alkyl group in which at least one hydrogen atom has been replaced by a fluorine atom. From the viewpoint of ensuring a favorable glass transition temperature (Tg) for the silsesquioxane resin and favorable solubility in the resist solvent, the number of carbon atoms within the alkyl group is preferably in a range of 1 to 8, and lower alkyl groups having 1 to 4 carbon atoms are more preferable he wishes.

Further, an increase in the number of hydrogen atoms substituted by fluorine atoms is preferable because it improves the transparency to high-energy light of not more than 200 nm and electron beams, and the most preferred groups are perfluoroalkyl groups in which all hydrogen atoms are replaced by fluorine atoms.

In the general formulas [1] and [2], the X groups may be the same group or different groups. In other words, the plurality of X groups are mutually independent.

In view of the ability to readily cleave the acid-cleavable, dissolution-inhibiting group, m must be an integer of 1 to 3, and is preferably 1.

Specific examples of the silsesquioxane resin preferably used include silsesquioxane resins containing structural units represented by the following general formulas [14] and [15].

[Formula 9]

In these formulas, R ¹ and R ^{2 are} as defined above. R ⁵ is a lower alkyl group, and preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group or an ethyl group. n is an integer from 1 to 8, and preferably from 1 to 2.

In other words, the general formulas [14] and [15] represent the general formulas [1] and [2] in those cases where R ^{3 is} a group represented by the formula [11] or [12] , R ^{4 is} a hydrogen atom, X is an alkyl group in which all the hydrogen atoms have been replaced by fluorine atoms, and m = 1. R ³ is most preferably the group of formula [11].

Of all the structural units constituting the silsesquioxane resin preferably used herein, the proportion of the structural units represented by the general formulas [1] and [2] is usually within a range of 30 to 100 mol%, and preferably from 60 to 100 mol%. In other words, the silsesquioxane resin may contain up to 40 mol% of structural units other than the structural units represented by the general formulas [1] and [2]. A description of these optional structural units other than the structural units represented by the general formulas [1] and [2] will be given below.

Further, the proportion of the structural units represented by the general formula [1] based on the combined total amount of structural units represented by the general formulas [1] and [2] is preferably within a range of 5 to 70 mol%, and more preferably from 10 to 40 mol%. The proportion of the structural units represented by the general formula [2] is preferably within a range of from 30 to 95 mol%, and more preferably from 60 to 90 mol%.

By ensuring that the proportion of the structural units represented by the general formula [1] falls within the above range, the proportion of acid-cleavable, dissolution-preventing groups is naturally determined and the change in solubility in alkali of the silsesquioxane resin after irradiation is set to an ideal value for a base resin of a positive resist composition.

[worin R' eine geradekettige oder verzweigte niedere Alkylgruppe und vorzugsweise eine niedere Alkylgruppe mit 1 bis 5 Kohlenstoffatomen darstellt]Provided that their inclusion does not affect the effects of the present invention, the silsesquioxane resin as the optional units described above may also contain structural units other than the structural units represented by the general formulas [1] and [2]. Examples of these optional units include alkylsilsesquioxane units which may be a lower alkyl group such as e.g. A methyl group, ethyl group, propyl group or butyl group as shown by the following general formula [17] used in silsesquioxane resins used in ArF excimer laser resist compositions. [Formula 10]

[wherein R 'represents a straight or branched lower alkyl group and preferably a lower alkyl group having 1 to 5 carbon atoms]

In cases where a structural unit represented by the general formula [17] is used, the proportion of the structural units represented by the general formula [1], based on the combined total amount of structural units, is represented by the general formulas [1], [2] and [17], generally within a range of from 5 to 30 mol%, and preferably from 8 to 20 mol%. The proportion of structural units represented by the general formula [2] is generally within a range of from 40 to 80 mol%, and preferably from 50 to 70 mol%, and the proportion of structural units represented by the general formula 17] is usually within a range of 1 to 40 mol%, and preferably 5 to 35 mol%.

There are no particular limitations on the weight-average molecular weight (Mw) (the value equivalent to polystyrene was determined by gel permeation chromatography, including all subsequent values) of the silsesquioxane resin preferably used in the present invention, although the value is preferably within a range of 2,000 to 15,000 and more preferably from 3,000 to 8,000. When the weight-average molecular weight is above this range, the solubility in the resist solvent deteriorates, whereas when it is below the above range, there is a fear of deterioration in the cross-sectional shape of the resist pattern.

Further, although there are no particular limitations on the ratio Mw / Mn (number-average molecular weight), this ratio is preferably in a range of 1.0 to 6.0, and more preferably 1.1 to 2.5. If this ratio is above this range, there is a risk of deterioration in both the resolution and the shape of the pattern.

The preparation of the silsesquioxane resin preferably used herein can be usually carried out using the general method used for the production of random polymers, and an example of the method is described below.

First, a single silicon-containing monomer giving the structural unit represented by the formula [2] or a mixture of two or more of such monomers is subjected to dehydration-condensation in the presence of a catalyst, thereby obtaining a polymer solution containing Contains polymer with a silsesquioxane as a backbone. Next, an amount of Br- (CH ₂ ) _m COOR ³ , which corresponds to 5 to 70 mol% of the aforementioned Si-containing monomer, in an organic solvent such. For example, tetrahydrofuran is dissolved and the resulting solution is added dropwise to the polymer solution, whereby an addition reaction is carried out, which converts -OR ⁴ in -O- (CH ₂ ) _m COOR ³ .

Further, in the case of a resin containing a structural unit represented by the formula [17], the preparation can be carried out in the same manner as above using an Si-containing monomer represented by the formula [2] structural unit and an Si-containing monomer giving the structural unit represented by the formula [17].

As described above, the silsesquioxane resin of the present invention preferably used in the present invention is effective in preventing the degassing phenomenon that may occur after irradiation during the formation of a resist pattern.

Further, because this silsesquioxane resin is a polymer containing as a skeleton a silsesquioxane structure consisting of structural units represented by the formulas [1] and [2] and, in some cases, the formula [17], The transparency of the resin to high-energy light of not more than 200 nm and electron beams are extremely high. Therefore, a positive resist composition containing silsesquioxane resin used in the present invention can be advantageously used for lithography using a light source having a shorter wavelength than that of even an ArF excimer laser, and used in a single-layer process for forming ultrafine resist. Patterns with linewidths of not more than 150 nm and even less than 120 nm can be used. Furthermore, by using such a positive resist composition as the upper layer in a two-layer resist laminate described below, methods for forming ultrafine resist patterns of not more than 120 nm and even 100 nm or less can be realized.

<< positive resist composition >>

Component (A)

A positive resist composition preferably used in the present invention comprises a resin component (A) which has an increased solubility in alkali when exposed to acid, and an acid generator component (B) which generates acid upon irradiation, wherein component (A) comprises an aforementioned silsesquioxane. Resin of the present invention (hereinafter referred to as the silsesquioxane resin (A1)) contains.

By using the silsesquioxane resin (A1) in the component (A), the degassing during the formation of the resist pattern can be prevented by using a positive resist composition containing the silsesquioxane resin (A1). Further, this positive-resist composition exhibits a high level of transparency to high-energy light of not more than 200 nm and electron beams, and enables the production of high-resolution patterns.

The component (A) may contain only the silsesquioxane resin (A1) or may also be a mixed resin containing other resins besides (A1). The proportion of (A1) within a mixed resin is preferably within a range of 50 to 95% by weight, and more preferably 70 to 90% by weight.

By ensuring that the proportion of the silsesquioxane resin (A1) is within the above range, superior prevention of the degassing phenomenon can be realized, and in the cases where a two-layer resist laminate is formed, the upper layer constitutes one excellent performance as a mask during the dry etching of the lower resist layer ready.

As the optional resin component (A2) other than (A1), any of the resins commonly used as base resins in chemically amplified resist compositions can be selected and used in accordance with the light source used during the formation of the resist pattern.

For example, in cases where an ArF excimer laser is used, a mixed resin having a resin component (A2) containing a structural unit (a1) derived from a (meth) acrylate ester is one by acid Cleavable, the dissolution-inhibiting group contains, because such a mixture allows an improvement in the heat resistance of the entire component (A) and also gives an excellent resolution.

As the resin (A2), resins containing a structural unit (a1) derived from a (meth) acrylate ester containing an acid-cleavable, dissolution-inhibiting group and a structural unit other than ( a1) but also derived from a (meth) acylate ester, wherein the proportion of structural units derived from (meth) acrylate esters is at least 80 mole%, and more preferably 90 mole% or above (and most preferably 100 mole%) prefers.

The term "(meth) acrylic acid" refers to either methacrylic acid or acrylic acid or both. Similarly, the term "(meth) acrylate" refers to either methacrylate or acrylate or both.

• – Strukturelle Einheiten, die sich von einem (Meth)Acrylatester ableiten, der eine Lactoneinheit (im Folgenden als (a2) oder (a2)-Einheiten bezeichnet) enthält
• – Strukturelle Einheiten, die sich von einem (Meth)Acrylatester ableiten, der eine polycyclische Gruppe mit einer alkoholischen Hydroxylgruppe (im Folgenden als (a3) oder (a3)-Einheiten bezeichnet) enthält.
• – Strukturelle Einheiten, die eine polycyclische Gruppe enthalten, die sich von der in Säure abspaltbaren, die Auflösung verhindernden Gruppe der (a1)-Einheiten, der Lacton-Einheit der (a2)-Einheiten und der polycyclischen Gruppe mit einer alkoholischen Hydroxylgruppe der (a3)-Einheiten unterscheidet (im Folgenden als (a4) oder (a4)-Einheiten).

Further, the resin (A2) preferably contains a combination of a plurality of monomer units different from the unit (a1) and provides a variety of different functions to provide the required levels of resolution, resistance to dry etching, and a fine pattern shape fulfill.

• Structural units derived from a (meth) acrylate ester containing a lactone moiety (hereinafter referred to as (a2) or (a2) moieties)
• Structural units derived from a (meth) acrylate ester containing a polycyclic group having an alcoholic hydroxyl group (hereinafter referred to as (a3) or (a3) units).
• - Structural units containing a polycyclic group consisting of the acid-cleavable, the dissolution-inhibiting group of (a1) units, the lactone unit of the (a2) units and the polycyclic group having an alcoholic hydroxyl group of (a3 ) Units (hereinafter referred to as (a4) or (a4) units).

The units (a2), (a3) and / or (a4) may be suitably combined in accordance with the characteristics required for the resin.

The component (A2) preferably contains the (a1) unit and at least one unit selected from the (a2), (a3) and (a4) units because such resins have superior resolution and shape of the resist pattern , Each of the units (a1) to (a4) may contain a combination of a plurality of different units.

In the component (A2), of the total number of moles of structural units derived from methacrylate esters and structural units derived from acrylate esters, the structural units derived from methacrylate esters, preferably 10 to 85 mol%, more preferably 20 to 80 mol%, whereas the structural units derived from acrylate esters are preferably 15 to 90 mol% and more preferably 20 to 80 mol%.

The following is a detailed description of each of the above units (a1) to (a4).

[(A1) units]

The (a1) unit is a structural unit derived from a (meth) acrylate ester containing an acid-cleavable, dissolution-inhibiting group.

There is no particular restriction on the acid-cleavable, dissolution-inhibiting group of (a1), provided that it exhibits an alkali-dissolving effect which renders the entire component (A2) insoluble in the alkali prior to irradiation but splits off under the action of acid generated after irradiation from the aforementioned component (B), whereby the entire component (A2) becomes soluble in alkali. In general, groups forming a cyclic or chain tertiary alkyl ester having the carboxyl group of (meth) acrylic acid, tertiary alkoxycarbonyl groups or chain alkoxyalkyl groups are mostly used.

As the acid dissociable, dissolution inhibiting group within (a1), an acid dissociable, dissolution inhibiting group containing an aliphatic polycyclic group can be advantageously used.

Examples of this polycyclic group include groups in which a hydrogen atom has been removed from a bicycloalkane, a tricycloalkane or a tetracycloalkane or the like which may be either unsubstituted or substituted with a fluorine atom or a fluoroalkyl group. Specific examples include groups in which a hydrogen atom of a polycycloalkane such as. As adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane has been removed. These types of polycyclic groups may be suitably selected from a variety of groups proposed for use with ArF resists. Among these groups, adamantyl groups, norbornyl groups and tetracyclododecanyl groups are preferred from the viewpoints of industrial availability.

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt und R²¹ eine niedere Alkylgruppe darstellt) [Formel 12]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt und R²² und R²³ jeweils unabhängig voneinander eine niedere Alkylgruppe darstellen) [Formel 13]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt und R²⁴ eine tertiäre Alkylgruppe darstellt) [Formel 14]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) [Formel 15]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt und R²⁵ eine Methylgruppe darstellt) [Formel 16]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt und R²⁶ eine niedere Alkylgruppe darstellt) [Formel 17]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) [Formel 18]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) [Formel 19]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt und R²⁷ eine niedere Alkylgruppe darstellt)Ideal monomer units for the (a1) units are shown below in [Formula 11] to [Formula 19]. [Formula 11]

(wherein R represents a hydrogen atom or a methyl group and R ^{21 represents} a lower alkyl group) [Formula 12]

(wherein R represents a hydrogen atom or a methyl group and R ²² and R ²³ each independently represent a lower alkyl group) [Formula 13]

(wherein R represents a hydrogen atom or a methyl group and R ^{24 represents} a tertiary alkyl group) [Formula 14]

(wherein R represents a hydrogen atom or a methyl group) [Formula 15]

(wherein R represents a hydrogen atom or a methyl group and R ^{25 represents} a methyl group) [Formula 16]

(wherein R represents a hydrogen atom or a methyl group and R ^{26 represents} a lower alkyl group) [Formula 17]

(wherein R represents a hydrogen atom or a methyl group) [Formula 18]

(wherein R represents a hydrogen atom or a methyl group) [Formula 19]

(wherein R represents a hydrogen atom or a methyl group and R ^{27 represents} a lower alkyl group)

Within the above formulas, the groups R ²¹ to R ²³ and R ²⁶ to R ²⁷ each preferably represent a straight-chain or branched lower alkyl group having 1 to 5 carbon atoms, and specific examples include a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group , Tertiary butyl group, pentyl group, isopentyl group and neopentyl group. From the viewpoint of industrial availability, a methyl group or an ethyl group is preferable.

Furthermore, R ^{24 represents} a tertiary alkyl group such as. A tertiary butyl group or a tertiary amyl group, although industrially a tertiary butyl group is preferred.

As the (a1) unit, of all the units described above, the structural units represented by the general formulas (I), (II) and (III) produce resist patterns having particularly superior transparency, resolution and resistance to dry etching, and therefore most preferred.

[(A2) units]

The (a2) unit contains a lactone unit and is therefore effective for improving the hydrophilicity with the developing solution.

An (a2) unit of the present invention may be any unit containing a lactone unit and copolymerizable with the other structural units of the component (A).

Examples of suitable monocyclic lactone units include groups in which a hydrogen atom has been removed from the γ-butyralactan. Further, examples of suitable polycyclic lactone units include groups in which a hydrogen atom has been removed from a lactone-containing polycycloalkane. In the lactone unit, the ring containing the -O-C (O) structure is counted as the first ring. Therefore, the case where the only ring structure is the ring containing the -O-C (O) structure is referred to as a monocyclic group, and groups containing other ring structures are referred to as polycyclic groups, regardless of the structure of the other rings.

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) [Formel 21]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) [Formel 22]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt)Ideal monomer units for the (a2) unit are shown below in the general formulas [Formula 20] to [Formula 22]. [Formula 20]

(wherein R represents a hydrogen atom or a methyl group) [Formula 21]

(wherein R represents a hydrogen atom or a methyl group) [Formula 22]

(wherein R represents a hydrogen atom or a methyl group)

Of the above units, in view of industrial availability, γ-butyrolactone esters of (meth) acrylic acid having an ester linkage at the α-carbon atom as shown in [Formula 22] or norbornane lactone esters such as those in [Formula 20] and [ Formula 21] shown, particularly preferred.

[(A3) units]

The (a3) unit is a structural unit derived from a (meth) acrylate ester containing a polycyclic group having an alcoholic hydroxyl group. Since the hydroxyl group of the polycyclic group containing an alcoholic hydroxyl group is a polar group, the use of this unit results in increased hydrophilicity for the whole component (A2) relative to the developing solution and an improvement in the solubility of the irradiated parts in alkali. Therefore, there is a favorable improvement in resolution when component (A2) contains (a3).

As the polycyclic group in the (a3) unit, any polycyclic group may be suitably selected from the various aliphatic polycyclic groups listed in the above description for the (a1) unit.

There are no particular restrictions on the alcoholic hydroxyl group-containing polycyclic group in the (a3) unit, and, for example, a hydroxyl group-containing adamantyl group can be advantageously used.

(worin n eine ganze Zahl von 1 bis 3 darstellt) In addition, when this hydroxyl group-containing adamantyl group is a group represented by the general formula (IV) shown below, the resistance to dry etching as well as the perpendicularity of the cross-sectional shape of the pattern, which are both desirable, are improved. [Formula 23]

(wherein n represents an integer of 1 to 3)

The (a3) unit may be any unit containing an aforementioned alcoholic hydroxyl group-containing polycyclic group and copolymerizable with the other structural units of the component (A2).

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt)Specifically, the structural units represented by the general formula (V) shown below are preferable. [Formula 24]

(wherein R represents a hydrogen atom or a methyl group)

[(A4) units]

In the (a4) unit, a polycyclic group "other than the acid-cleavable dissolution-preventing group, the lactone unit and the polyhydric alcohol group-containing polycyclic group" means the polycyclic one in the component (A2) Group of (a4) unit is a polycyclic group which the acid-cleavable, the dissolution-preventing group of the (a1) unit, the lactone unit of the (a2) unit or the alcoholic hydroxyl group-containing polycyclic group of (a3 ) Unit, not duplicated, and also means that the (a4) unit contains the acid dissociable, dissolution inhibiting group of the (a1) unit, the lactone unit of the (a2) unit or the alcoholic hydroxyl group-containing group Polycyclic group of the (a3) unit, which represent the component (A2), not supported.

There are no particular restrictions on the polycyclic group of the (a4) unit provided that it is selected so as not to duplicate any of the structural units used in units (a1) to (a3) of a single component (A2). For example, as the polycyclic group in the (a4) unit, the same aliphatic polycyclic groups as described in the above Description of the (a1) unit can be used, and any of the variety of materials conventionally used for ArF positive resist materials can be used.

From the viewpoint of industrial availability, one or more groups selected from tricyclodecanyl, adamantyl groups and tetracyclododecanyl groups are preferable.

The (a4) unit may be any unit containing an aforementioned polycyclic group and copolymerizable with the other structural units of the component (A).

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) [Formel 26]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) [Formel 27]

(worin R ein Wasserstoffatom oder eine Methylgruppe darstellt) Preferred examples of (a4) are shown below in [Formula 25] to [Formula 27]. [Formula 25]

(wherein R represents a hydrogen atom or a methyl group) [Formula 26]

(wherein R represents a hydrogen atom or a methyl group) [Formula 27]

(wherein R represents a hydrogen atom or a methyl group)

In a positive resist composition of the present invention, compositions of component (A2) in which the (a1) unit is 20 to 60 mol%, and preferably 30 to 50 mol% based on the combined total amount of all the structural units of the component (A2), an excellent resolution and are therefore preferred.

Further, compositions in which the (a2) unit constitutes 20 to 60% by mol, and preferably 30 to 50% by mol of the total of all the structural units of the component (A2) are excellent in resolution and are therefore preferred.

Furthermore, in cases where the (a3) unit is used, compositions in which the (a3) unit contains from 5 to 50 mol% and preferably from 10 to 40 mol% of the total of all structural units of component (A2) an excellent shape of the resist pattern and are therefore preferred.

In cases where the (a4) unit is used, compositions in which the (a4) unit constitutes 1 to 30 mol%, and preferably 5 to 20 mol% of the total of all the structural units of the component (A2) , a superior resolution for isolated patterns to semi-dense patterns, and are therefore preferred.

The (a1) unit may be suitably combined with at least one unit selected from the (a2), (a3) and (a4) units in accordance with the desired characteristics, and a tertiary polymer containing a (a1) unit together with (a2) and (a3) units is particularly preferable because it shows an excellent shape of the resist pattern, irradiation spectrum, heat resistance and resolution. In such a polymer, the respective proportions of each of the structural units (a1) to (a3) are preferably from 20 to 60 mol% for (a1), from 20 to 60 mol% for (a2), and from 5 to 50 mol% for (a3).

Further, there are no particular limitations on the weight-average molecular weight of the component (A2) in the present invention, although the values are usually within a range of 5,000 to 30,000, and preferably 8,000 to 20,000. If the molecular weight is higher than this range, the solubility of the component in the resist solvent deteriorates, whereas if the molecular weight is too small, there is a fear of deterioration of the resistance to dry etching and the shape of the cross section of the resist pattern.

The resin component (A2) in the present invention can be easily obtained by a conventional radical polymerization of the monomer corresponding to (a1) unit and, if necessary, monomers containing the (a2), (a3) and (a4) Units, wherein an initiator for the radical polymerization such. B. azobisisobutyronitrile (AIBN) is used.

Component (B)

As the component (B), a compound of known materials which are used as acid generators in conventional chemically amplified resists can be suitably selected.

Examples of suitable compounds for component (B) include onium salts such as e.g. As diphenyliodonium trifluoromethanesulfonate, (4-methoxyphenyl) phenyliodonium trifluoromethanesulfonate, bis (p-tert-butylphenyl) iodonium trifluoromethanesulfonate triphenylsulfonium trifluoromethanesulfonate, (4-methoxyphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-methylphenyl) diphenylsulfoniumnonafluorbutansulfonat, (p-tert-butylphenyl) diphenylsulfonium, Diphenyliodoniumnonafluorbutansulfonat, Bis (p-tert-butylphenyl) iodonium nonafluorobutanesulfonate, triphenylsulfonium nonafluorobutanesulfonate, (4- (trifluoromethylphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-trifluoromethylphenyl) diphenylsulfonium nonafluorobutanesulfonate, and tri (p-tert-butylphenyl) sulfonium trifluoromethanesulfonate.

Of these onium salts, triphenylsulfonium salts are resistant to decomposition and are unlikely to produce organic gases. Therefore, they are preferred. The amount of triphenylsulfonium salts based on the total amount of the component (B) is preferably within a range of 50 to 100 mol%, and more preferably 70 to 100 mol%, and most preferably 100 mol%.

Of the above onium salts, iodonium salts may give rise to the formation of organic gases containing iodine.

[worin R¹¹, R¹² und R¹³ jeweils unabhängig voneinander ein Wasserstoffatom, eine niedere Alkylgruppe mit 1 bis 8 und vorzugsweise 1 bis 4 Kohlenstoffatomen oder ein Halogenatom wie zum Beispiel ein Chlor-, Fluor- oder Bromatom darstellen; und p eine ganze Zahl von 1 bis 12 und vorzugsweise von 1 bis 8 und noch mehr bevorzugt von 1 bis 4 darstellt]Further, of the triphenylsulfonium salts, triphenylsulfonium salts represented by the general formula [16] given below containing a perfluoroalkylsulfonate ion as an anion provide improved levels of sensitivity and are therefore preferred. [Formula 28]

[wherein R ¹¹ , R ¹² and R ¹³ each independently represent a hydrogen atom, a lower alkyl group having 1 to 8 and preferably 1 to 4 carbon atoms, or a halogen atom such as a chlorine, fluorine or bromine atom; and p represents an integer of from 1 to 12, and preferably from 1 to 8, and more preferably from 1 to 4]

The component (B) can be used either alone or as a combination of two or more different compounds.

The amount of component (B) used is usually within a range of 0.5 to 30 parts by weight, and preferably 1 to 10 parts by weight, based on 100 parts by weight of component (A). At amounts of less than 0.5 part by weight, the formation of the pattern does not satisfactorily occur, whereas if it exceeds 30 parts by weight, it becomes difficult to obtain a uniform solution and there is a fear of deterioration in storage stability.

A particularly preferred positive resist composition according to one embodiment of the present invention can be prepared by dissolving component (A) and component (B) together with any of the optional components described below in an organic solvent.

The organic solvent may be any solvent capable of dissolving component (A) and component (B) to produce a uniform solution and one or more solvents selected from known materials such as those used as solvents chemically amplified resists used may be used.

In a photoresist composition used in the present invention, the amount of the organic solvent component is generally sufficient to produce a concentration of the solid fraction within the resist composition of 3 to 30% by weight, the actual value being adjusted in accordance with the thickness of the resist film becomes.

Specific examples of the solvent include ketones such as. Acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone and 2-heptanone; polyhydric alcohols and derivatives thereof, such as. Ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol or the monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether of dipropylene glycol monoacetate; cyclic ethers such as For example dioxane; and esters such. Methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate and ethylethoxypropionate. These organic solvents may be used alone or as a mixed solvent of two or more different solvents.

Further, in a positive resist composition of the present invention for improving the shape of the resist pattern and the latent image stability after the irradiation formed by the pattern-wise irradiation of the resist layer, a well-known one may also be used Amine and preferably a secondary lower aliphatic amine or tertiary lower aliphatic amine or an organic acid such. For example, an organic carboxylic acid or a phosphorus oxo acid or a derivative thereof may be added as a quencher.

Here, a lower aliphatic amine means an alkyl or alkyl alcohol amine having not more than 5 carbon atoms, and examples of these secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, tri-n-propylamine, tripentylamine, diethanolamine and triethanolamine. and alkanolamines such. B. triethanolamine are particularly preferred. These can be used either alone or as a combination of two or more different compounds. These amines are generally added in an amount of 0.01 to 2.0% by weight based on the amount of the component (A). As the organic carboxylic acid, malonic acid, citric acid, malic acid, succinic acid, benzoic acid and salicylic acid are ideal.

Examples of suitable phosphorus oxo acids or derivatives thereof include phosphoric acid or derivatives thereof, such as e.g. Esters, including phosphoric acid, di-n-butyl phosphate and diphenyl phosphate; Phosphonic acid or derivatives thereof such. Esters, including phosphonic acid, dimethyl phosphonate, di-n-butyl phosphonate, phenyl phosphonic acid, diphenyl phosphonate and dibenzyl phosphonate; and phosphinic acid or derivatives thereof such. As esters, including phosphinic acid and phenylphosphinic acid and among these phosphonic acid is particularly preferred.

The organic acid is usually used in an amount within a range of 0.01 to 5.0 parts by weight based on 100 parts by weight of the component (A). These acids can be used either alone or as a combination of two or more different compounds. These organic acids are preferably used in an amount corresponding to not more than an equimolar ratio with the above amines.

Other miscible additives may also be added to a positive resist composition of the present invention depending on necessity, including additive resins for improving the properties of the resist film, surface-active agents for improving easiness of application, inhibitors for dissolution, plasticizers, Stabilizers, colorants and halation preventing agents.

By using a positive resist composition having the above-described kind of structure, the degassing after the irradiation at the time of forming the resist pattern can be reduced. Furthermore, the composition also has excellent transparency to high-energy light of not more than 200 nm and electron beams, and provides a high level of resolution.

<< resist laminate >>

A resist laminate which can be obtained according to the present invention includes a lower resist layer which is insoluble in the alkali developing solution but can be etched dry, and an upper resist layer formed of a positive resist composition of the present invention laminated on the surface of a support.

As the support, conventional materials may be used without any particular limitations, and suitable examples include substrates for electronic components as well as substrates on which a predetermined wiring pattern has already been formed.

Specific examples of suitable substrates include substrates based on metals such. As silicon wafers, copper, chromium, iron and aluminum as well as glass substrates.

Suitable materials for the wiring pattern include copper, aluminum, nickel and gold.

The lower resist layer is an organic film which is insoluble in the alkali developing solution used for development after irradiation but can be etched by conventional dry etching.

With this type of lower resist layer, conventional photolithography techniques are used first to irradiate only the upper resist layer and then to develop with alkali to form a resist pattern. By then using this resist pattern as a mask to perform the etching of the lower resist layer, the resist pattern of the upper resist layer is transferred to the lower resist layer. As a result, a resist pattern having a high aspect ratio can be formed without causing the resist pattern to collapse the pattern.

The resist material for forming the lower resist layer, though referred to as a resist, does not require the photosensitivity required for the upper resist layer and may use the kind of material conventionally used as a base material in the production of semiconductor elements and liquid crystal devices. Display elements is used.

Further, since the resist pattern of the upper resist layer has to be transferred to the lower resist layer, the lower resist layer should preferably be formed of a material that can be etched by oxygen plasma etching.

As this material, materials containing at least one resin selected from a group consisting of novolak resins, acrylic resins and soluble polyimides as the primary component are preferable because they can be readily etched by an oxygen plasma treatment and also have a good resistance to fluorocarbon based gases, which can be used in the following processes for tasks such. B. the etching of the silicon substrate can be used.

Of these materials, novolak resins and acrylic resins containing an alicyclic region or an aromatic ring in a side chain are inexpensive, widely used, and exhibit excellent resistance to dry etching in subsequent processes, and are therefore preferred.

As the novolak resin, any resins conventionally used in positive resist compositions can be used, and positive resists for i-line irradiation or g-lines containing a novolak resin as the primary component can also be used.

A novolak resin is a resin obtained by an addition condensation between an aromatic compound containing a phenolic hydroxyl group (hereinafter simply referred to as a phenol) and an aldehyde in the presence of an acidic catalyst.

Examples of the phenol used include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-butylphenol, m-butylphenol, p-butylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, p-phenylphenol, Resorcinol, hydroquinone, hydroquinone monomethyl ether, pyrogallol, fluoroglucinol, hydroxydiphenyl, bisphenol A, gallic acid, gallic acid esters, α-naphthol and β-naphthol.

Further, examples of the aldehyde include formaldehyde, furfural, benzaldehyde, nitrobenzaldehyde and acetaldehyde.

There are no particular restrictions on the catalyst used in the addition condensation reaction, and suitable acid catalysts include hydrochloric acid, nitric acid, sulfuric acid, formic acid, oxalic acid and acetic acid.

The weight-average molecular weight of the novolak resin is usually within a range of from 3,000 to 10,000, and preferably from 6,000 to 9,000, and most preferably from 7,000 to 8,000. When the weight-average molecular weight is less than 3,000, the resin tends to lose the resistance to the alkali-developing solution. On the other hand, if the weight-average molecular weight exceeds 10,000, it becomes more difficult to dry-etch the resin, which is undesirable.

Novolac resins for use in the present invention may use commercially available resins.

As the acrylic resin, any of the resins conventionally used in positive resist compositions may be used, and suitable examples include acrylic resins containing a structural unit derived from a polymerizable compound having an ether linkage and a structural unit derived from a polymerizable compound containing a carboxyl group is derived.

Examples of the polymerizable compound containing an ether linkage include (meth) acrylic acid derivatives containing both an ether linkage and an ester linkage, such as, for example, the like. For example, 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethylcarbitol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate and tetrahydrofurfuryl (meth) acrylate. These compounds can be used either alone or as a combination of two or more different compounds.

Examples of the polymerizable compound containing a carboxyl group include monocarboxylic acids such as e.g. Acrylic acid, methacrylic acid and crotonic acid; Dicarboxylic acids such. Maleic acid, fumaric acid and itaconic acid; and compounds containing both a carboxyl group and an ester linkage, such as e.g. 2-methacryloyloxyethylsuccinic acid, 2-methacryloyloxyethylmaleic acid, 2-methacryloyloxyethylphthalic acid and 2-methacryloyloxyethylhexahydrophthalic acid, though preferred of these are acrylic acid and methacrylic acid. These compounds can be used either alone or as a combination of two or more different compounds.

The soluble polyimide refers to polyimides that can be converted to liquid form in the type of organic solvents described above.

In a resist laminate of the present invention, considering the ideal balance between the desired aspect ratio and the throughput, which is affected by the time required for the dry etching of the lower resist layer, the combined thickness of the upper resist layer and the The lower resist layer is preferably not more than 15 μm in total and is preferably from 0.1 to 5 μm.

The thickness of the upper resist layer is preferably within a range of 50 nm to 1 μm, and more preferably from 70 to 250 nm.

By ensuring that the thickness of the upper resist layer is within this range, a resist pattern having a high level of resolution can be formed, and also a satisfactory level of resistance to dry etching can be obtained.

The thickness of the lower resist layer is preferably within a range of 100 nm to 14 μm, and more preferably from 200 to 500 nm. By ensuring that the thickness of the lower resist layer is within this range, a resist pattern may be formed can be formed with a high aspect ratio, whereby a satisfactory level for the resistance to etching can be ensured in subsequent etching of the substrate.

The resist laminate obtainable according to the present invention includes both resist laminates in which a resist pattern has been formed in the upper resist layer and the lower resist layer, as well as laminates in which no resist is formed. Pattern has been formed.

<< Method for forming resist patterns >>

A method for forming a resist pattern used in the present invention may be carried out, for example, in the manner described below.

First, a resist composition or a resin solution for forming the lower resist layer is applied to the surface of a substrate such as a spinner or the like by using a spinning disk or the like. A silicon wafer, and a prebake treatment is then carried out, preferably at a temperature of 200 to 300 ° C for a period of 30 to 300 seconds, and preferably 60 to 180 seconds, whereby a lower resist layer is formed.

An organic or inorganic reflection-reducing film may also be provided between the lower resist layer and the upper resist layer.

Next, a positive resist composition used in the present invention is applied to the lower resist layer using a spinner or the like. A pre-bake treatment is then conducted at a temperature of 80 to 150 ° C for a period of 40 to 120 seconds, and preferably 60 to 90 seconds, thereby forming an upper resist layer and completing the production of a resist laminate of the present invention ,

The resist laminate is then selectively irradiated by an ArF irradiation apparatus or the like by irradiating the ArF excimer laser light through a desired mask pattern, and post exposure baking (PEB) is then performed under temperature conditions of 80 to 150 ° C for 40 to 120 seconds and preferably carried out for 60 to 90 seconds.

Subsequently, the resist laminate using an alkali developer solution such. B. an aqueous solution of tetramethylammonium hydroxide with a concentration of 0.05 to 10 weight percent, and preferably from 0.05 to 3 weight percent developed. In this way, a resist pattern (I) faithful to the mask pattern can be formed in the upper resist layer.

As a light source used for the irradiation, an ArF excimer laser is particularly effective, but light sources of longer wavelength such as. As a KrF excimer laser or light sources of shorter wavelength such. As an F ₂ -Excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), electron beams or irradiation with X-rays or soft X-rays can also be used efficiently.

Next, the obtained resist pattern (I) is used as a mask pattern for performing dry etching of the lower resist layer, thereby forming a resist pattern (II) in the lower resist layer.

As a method for dry etching conventional methods including chemical etching such. B. down-flow etching or chemical dry etching; physical etching such. Sputter etching or ion beam etching; or chemical-physical etching such. B. RIE (reactive ion etching) can be used.

The most commonly used type of dry etching is RIE with parallel plates. In this method, a resist laminate is first placed inside the chamber of the RIE device and the required etching gas introduced. A high frequency voltage is then supplied to the chamber, between an upper electrode and the resist laminate holder, which is positioned parallel to the electrode, and this causes generation of a caustic gas plasma. The plasma contains charged particles such. B. positive and negative ions and electrons as well as electrically neutral active nuclei. As these etch nuclei are absorbed on the lower resist layer, a chemical reaction occurs and the resulting reaction product breaks away from the surface and is externally discharged, thereby progressing the etching.

As the etching gas, oxygen or sulfur dioxide or the like is possible, although oxygen is preferable, since oxygen plasma etching provides a high level of dissolution, the silsesquioxane resin (A1) preferably used herein exhibiting favorable resistance to oxygen plasma etching and oxygen plasma also becomes widely used used.

According to a method of forming a resist pattern, the degassing phenomenon which may occur after irradiation during the formation of a resist pattern is almost absent. Furthermore, the shape of the resist pattern formed by using such a method has a high aspect ratio, does not suffer collapse of the pattern, and provides a high degree of perpendicularity. Furthermore, a method of forming a resist pattern of the present invention enables the formation of resist patterns having ultra-fine widths of not more than 100 nm and even 65 nm or less when high-energy light of not more than 200 nm such as 200 nm. B. ArF excimer laser or an electron beam is used.

<< Positive Resist Composition Containing Silsesquioxane Resin and Method of Forming Resist Pattern Using This Positive Resist Composition >>

An advantageous use of the positive resist composition is disclosed in the immersion lithography method (also known as immersion exposure) disclosed in the aforementioned Non-Patent Document 1, Non-Patent Document 2 and Non-Patent Document 3. This is a method in which, during irradiation, the area between the lens and the resist layer disposed on the surface of the wafer, which is usually sealed with air or an inert gas such as e.g. B. nitrogen has been filled with a solvent such as. As pure water or an inert liquid based on fluorine, which has a higher refractive index than the refractive index of air is filled. By filling this area with this type of solvent, it is claimed that higher resolutions can be obtained that correspond to those obtained using a shorter wavelength or a larger NA lens when the same wavelength of the irradiation light source is used without Reduction in the depth of the focusing area.

Using this type of immersion lithography, resist patterns with higher resolution and superior depth of field can be formed at low cost using lenses mounted in a conventional apparatus, and therefore, this method attracts considerable attention.

In other words, according to the present invention, a positive resist composition used in a method of forming a resist pattern including an immersion lithography step. The sensitivity with which a 1-nm line-and-space resist pattern of 130 nm was formed by a normal irradiation lithography method using a light source having a wavelength of 193 nm is referred to as X1, and the sensitivity with an identical 1: 1 line-and-space resist pattern of 130 nm is formed by a simulated immersion lithography method, comprising a step of contacting an immersion lithography solvent with the resist film between the selective irradiation step and the post exposure baking (PEB) step of a normal irradiation lithography process using a light source having a wavelength of 193 nm, referred to as X2, the resist composition is a positive resist composition contains a silsesquioxane resin as the resin component for which the absolute value of [(X 2 / X 1) -1] x 100 does not m is more than 8.0.

More specifically, immersion lithography is used in a resist pattern forming method in which, during the immersion lithography step, the area between the resist layer formed of a positive resist composition containing the aforementioned silsesquioxane resin is formed , and the lens at the lowermost point of the irradiation device is filled with a solvent having a higher refractive index than the refractive index of air.

As the silsesquioxane resin, preferred are resins containing at least one silsesquioxane unit containing an acid dissociable, dissolution inhibiting group and a silsesquioxane unit containing an alcoholic hydroxyl group. Silsesquioxane resins which additionally contain an alkyl silsesquioxane moiety are also preferred. Particularly preferred resins include the silsesquioxane resins of the first aspect of the present invention.

When the sensitivity with which a 1: 1 line-and-space resist pattern of 130 nm is formed by a normal irradiation lithography method using a light source having a wavelength of 193 nm is denoted by X1 and the sensitivity with which a 1: 1 line-and-space resist pattern of 130 nm is formed by a simulated immersion lithography method in which a step of bringing a solvent for immersion lithography into contact with the resist film is interposed between the step of selective scanning Irradiation and the step of the subsequent baking (post exposure baking (PEB)) of a normal irradiation lithography process using a light source having a wavelength of 193 nm, referred to as X2, then the absolute value of [(X2 / X1) -1] x 100 at a value of not more 8.0 can be maintained by preparing a positive resist composition containing a resin component containing this type of silsesquioxane resin.

Assuming that this absolute value is not more than 8.0, the resist is ideally suited for use with immersion lithography. In particular, the resist is resistant to any harmful effects of the immersion solvent, thereby enabling formation of a resist having excellent sensitivity and shape of the resist pattern profile. The smaller this absolute value is, the better, and values of 5 or less are preferred, with values of not more than 3 and as close to zero as most desirable.

When used as a resin component of this positive resist composition is a mixed resin containing the silsesquioxane resin and a resin component (A2) containing a structural unit (a1) derived from a (meth) acrylate ester, one by acid Cleavable, dissolution-inhibiting group contains, as in the second aspect of the present invention, then the dissolution and the heat resistance can be advantageously improved.

A positive resist composition used in the present invention is useful as a positive resist composition used in a resist pattern forming method involving an immersion lithography step. This immersion lithography is a method in which the area between the resist layer formed of the positive resist composition and the lens at the lowest point of the irradiation apparatus is filled with a solvent having a larger refractive index than the refractive index of air.

Furthermore, this type of positive resist composition can also be used in a method of forming a resist pattern including the above type of immersion lithography step.

In the first aspect of the present invention, the normal irradiation lithography method using a light source having a wavelength of 193 nm refers to a conventional lithography method, that is, a conventional lithography method. H. individual steps for the application of the resist, the prebake, the selective irradiation, the post-exposure baking and the development with alkali, which is carried out using an ArF excimer laser with a wavelength of 193 nm as the light source, wherein a normal irradiation is performed when the area between the lens of the irradiation apparatus and the resist layer disposed on the surface of the wafer is exposed to air or an inert gas such as air. B. nitrogen is filled. In some cases, a post-bake step may also be provided following development with alkali. An organic or inorganic reflection-reducing film may also be provided between the substrate and the deposited layer of the resist composition.

The sensitivity X1 at which a 130 nm 1: 1 line-and-space resist pattern (hereinafter abbreviated as "130 nm L & S") is formed by this type of normal irradiation lithography method refers to an irradiation dose for formation a 130 nm L & S widely used by professionals in the field and is self-explanatory.

To briefly describe this sensitivity for the sake of completeness, the irradiation dose is plotted on the horizontal axis, the resist linewidth formed using this irradiation dose is plotted on the vertical axis, and a logarithmic approximation curve is plotted from this plot using the Obtained least squares method.

The formula is represented by Y = aLoge (X1) + b, where X1 represents the irradiation dose, Y represents the resist line width, and a and b are constants. When this formula is rearranged and converted into a formula representing X1, the formula X1 = Exp [(Y-b) / a] is obtained. If the value Y = 130 (nm) is introduced into this formula, then the calculated ideal sensitivity X1 can be determined.

The conditions during this process, namely the rate of rotation during the application of the resist, the prebake temperature, the irradiation conditions, the post-irradiation baking conditions, and the alkali development conditions, can each be set to conventionally used conditions and are self-explanatory of formation a 130 nm L & S. Specifically, an 8-inch diameter silicon wafer is used as the substrate Specifically, the rotational speed is set at 1,000 to about 4,000 rpm or more specifically at about 1,500 to 3,500 rpm or even more specifically at about 2,000 rpm, and the prebake temperature is set within a range of 70 to 140 ° C., and preferably 95 to 110 ° C (the adjustment of the temperature to a level which allows a 1: 1 ratio for a 130 nm line-and-space pattern will be understood by those skilled in the art). This allows a resist film having a diameter of 6 inches with a (resist) film thickness of 80 to 250 nm or more specifically of 150 nm, which is formed concentrically on the surface of the substrate.

The irradiation conditions include irradiation through a mask using an irradiation apparatus having an ArF excimer laser with a wavelength of 193 nm manufactured by Nikon Corporation or Canon Inc. or the like (NA = 0.60) or more specifically, the irradiation apparatus NSR-S302 (manufactured by Nikon Corporation, NA (numerical aperture) = 0.60, 2/3 annular exposure) was used. A normal binary mask is used as a mask in selective irradiation. A phase shift mask can also be used as a mask.

The baking after irradiation uses a temperature within a range of 70 to 140 ° C, and preferably 90 to 100 ° C (setting the temperature to a level giving a 1: 1 ratio for a 130 nm line-and-line). Space pattern is obvious to those skilled in the art), and conditions for development with alkali include immersing the substrate in a developer solution containing 2.38 weight percent TMAH (tetramethylammonium hydroxide) at a temperature of 23 ° C for a period of time from 15 to 90 seconds or more specifically 60 seconds and then rinse the substrate with water.

In addition, the simulated immersion lithography method refers to a method in which a step of contacting an immersion lithography solvent with the resist film between the selective irradiation step and the post exposure baking (PEB) step of a lithography process normal irradiation using the same 193 nm ArF excimer laser described above as the light source.

Specifically, the simulated method includes sequential steps for resist application, prebake, selective irradiation, a step of contacting the immersion lithography solvent with the resist film, baking after irradiation, and development with alkali. In some cases, a step of subsequent baking after development with alkali may also be provided.

The term "contacting" may include immersing the selectively exposed resist film deposited on the surface of a substrate in the immersion lithography solvent, or may include spraying the immersion lithography solvent onto the resist in the form of a shower. The temperature during this step is preferably 23 ° C. When the solvent is sprayed like a shower, the substrate may be rotated at a speed of 300 to 3,000 rpm, and preferably 500 to 2,500 rpm.

The conditions for the above-described contacting are as follows. Pure water is dropped on the center of the substrate from a rinsing nozzle while the wafer and the applied irradiated resist film are rotated; the rotational speed of the substrate on which the resist is formed: 500 rpm; Solvent: pure water; Rate of dropwise addition of the solvent: 1.0 L / min; the time for the solvent to drop: 2 to 5 minutes; Temperature when contacting solvent and resist: 23 ° C.

The sensitivity X2 at which a 130 nm L & S resist pattern is formed using this type of simulated immersion lithography method is similar to the value for X1 described above since it represents the exposure dose to form the L & S, which is one of skill in the art widely used value.

The conditions during this process (the rate of rotation during resist application, prebake temperature, irradiation conditions, post-blast baking conditions, and alkali development conditions) are also similar to the case of X1 described above.

In the first aspect of the present invention, the absolute value of [(X2 / X1) -1] x 100 must be not more than 8.0, and this absolute value is understood when the values of X2 and X1 are determined in the manner described above become.

Further, in a second aspect of the present invention, it may be preferable to perform the immersion lithography with a protective film formed of a fluorine-based resin on the surface of the resist film. In other words, first, the resist film is provided on the substrate. Subsequently, a protective film is applied on the surface of the resist film, and an immersion lithography liquid is then brought into direct contact with the protective film. The resist film is then selectively irradiated through the liquid and the protective film, and the baking after the irradiation is then performed. Subsequently, the protective film is removed and the resist film is then developed to form a resist pattern.

Desirable characteristics for the protective film include favorable transparency to the irradiation light; the protective film must be substantially incompatible with the liquid used for immersion lithography and must not undergo mixing with the resist film. The protective film must also have a good adhesion and a favorable removability from the resist film. Examples of protective materials which can form a protective film provided with the above characteristics include compositions obtained by dissolving a fluorine-based resin in a fluorine-based solvent.

As the fluorine-based resin, chain-like perfluoroalkyl polyethers, cyclic perfluoroalkyl polyethers, polychlorotrifluoroethylene, polytetrafluoroethylene, copolymers of tetrafluoroethylene and perfluoroalkoxyethylenes, and copolymers of tetrafluoroethylene and hexafluoropropylene can be used.

From a practical point of view, commercially available products including chain-type perfluoroalkyl polyethers such as e.g. B. Demnum S-20, Demnum S-65, Demnum S-100 and Demnum S-200 (all manufactured by Daikin Industries, Ltd.) and cyclic perfluoroalkyl polyethers such as e.g. For example, the Cytop series (manufactured by Asahi Glass Co., Ltd.), Teflon (R) -AF1600 and Teflon (R) -AF2400 (both manufactured by DuPont) can be used.

Of the above fluorine-based resins, mixed resins containing a chain-type perfluoroalkylpolyether and a cyclic perfluoroalkylpolyether are ideal.

As the above-mentioned fluorine-based solvent, any solvent capable of dissolving the above fluorine-based resins can be used without any particular limitations, and suitable examples include fluorine-based solvents including perfluoroalkane or perfluorocycloalkane such as fluorine. As perfluorohexane and perfluoroheptane, perfluoroalkenes in which within the above alkanes a double bond remains, as well as perfluorocycloether such. Perfluorotetrahydrofuran and perfluoro (2-butyltetrahydrofuran), perfluorotributylamine, perfluorotetrapentylamine and perfluorotetrahexylamine.

Further, other organic solvents or surfactants or the like having a proper co-solubility with these fluorine-based solvents may be appropriately blended in the solvent.

There are no particular restrictions on the concentration of the fluorine-based resin, provided that it is within a range which enables the formation of a film. Considering factors such as ease of application, the concentration is preferably within a range of 0.1 to 30% by weight.

An ideal material for a protective film can be prepared by dissolving a mixed resin containing a chain-type perfluoroalkylpolyether and a cyclic perfluoroalkylpolyether in perfluorotributylamine.

As the solvent for removing the protective film, the same fluorine-based solvents as described above can be used.

There are no particular limitations on the irradiation wavelength used in the fifth and sixth aspects of the present invention, and the irradiation may be carried out using a KrF excimer laser, an ArF excimer laser, an F ₂ laser, or other radiation such as radiation. EUV (extreme ultraviolet), VUV (vacuum ultraviolet), electron beams, soft X-rays or X-rays, although an ArF excimer laser is particularly preferred.

Examples

The following is a detailed description of the present invention based on a number of examples, although the present invention is by no means limited to these examples. Unless otherwise noted, blending levels are in weight percent.

• (1) Bedingungen zur Bildung des aufgebrachten Resist-Films Substrat: 8-Zoll Silizium-Wafer; Methode der Aufbringung des Resists: Aufbringung unter Verwendung einer Drehscheibe („spinner”) auf ein Substrat, das sich mit 2.000 U/min dreht; Größe des aufgebrachten Resist-Films: 6 Zoll Durchmesser, konzentrisch mit dem Substrat, Dicke 150 nm; Bedingungen beim Vorbacken: entweder 90 Sekunden bei 110°C (Beispiel 5) oder 60 Sekunden bei 95°C (Beispiel 7); Bedingungen für die selektive Bestrahlung: Bestrahlung durchgeführt unter Verwendung einen ArF-Excimer-Lasers (193 nm) (Bestrahlungsgerät NSR-S302B, hergestellt von Nikon Corporation, NA (numerische Apertur) = 0,60, 2/3 ringförmige Bestrahlung).
• (2) Bedingungen für den Kontakt zwischen dem aufgebrachten Resist-Film und dem Lösungsmittel Umdrehungsgeschwindigkeit des Substrats: 500 U/min; Lösungsmittel: Wasser; Geschwindigkeit des Tropfens: 1,0 l/min; Zeit für das Tropfen des Lösungsmittels: 2 Minuten oder 5 Minuten Temperatur beim Kontakt zwischen Lösungsmittel und Resist: 23°C.
• (3) Bedingungen für die Bildung des Resistmusters Bedingungen für das Backen nach der Bestrahlung: 90 Sekunden bei 90°C (Beispiel 5) oder 60 Sekunden bei 90°C (Beispiel 7); Bedingungen für die Entwicklung mit Alkali: 60 Sekunden Entwicklung bei 23°C in einer wässrigen Lösung mit 2,38 Gewichtsprozent Tetramethylammoniumhydroxid.

In the following examples, the conditions for the simulated immersion lithography and the sensitivity measurements are the following unless otherwise noted.

• (1) Conditions for Forming the Applied Resist Film Substrate: 8-inch silicon wafer; Method of applying the resist: application using a spinner on a substrate rotating at 2,000 rpm; Size of the applied resist film: 6 inches in diameter, concentric with the substrate, thickness 150 nm; Prebake conditions: either 90 seconds at 110 ° C (Example 5) or 60 seconds at 95 ° C (Example 7); Conditions for Selective Irradiation: Irradiation performed using an ArF excimer laser (193 nm) (irradiation apparatus NSR-S302B, manufactured by Nikon Corporation, NA (numerical aperture) = 0.60, 2/3 annular irradiation).
• (2) Conditions for the contact between the applied resist film and the solvent: Rotational speed of the substrate: 500 rpm; Solvent: water; Velocity of the drop: 1.0 l / min; Time for the solvent to drip: 2 minutes or 5 minutes of solvent-to-resist contact temperature: 23 ° C.
• (3) Conditions for forming the resist pattern Post-irradiation baking conditions: 90 seconds at 90 ° C (Example 5) or 60 seconds at 90 ° C (Example 7); Conditions for the development with alkali: Development for 60 seconds at 23 ° C in an aqueous solution with 2.38 weight percent tetramethylammonium hydroxide.

Production Example 1

20.0 g of hexafluoroisopropanolnorbornene, 0.02 g of a 20% by weight solution of chloroplatinic acid in isopropanol and 30 g of tetrahydrofuran were poured into a 200 ml flask and the mixture was heated to 70 ° C with stirring. 9.2 g of tetrachlorosilane were then added dropwise to the solution over a period of 15 minutes. After stirring for additional 5 hours, the mixture was distilled to give 15 g of hexafluoroisopropanol norbornyltrichlorosilane (a silicon-containing monomer represented by the formula [29] shown below).

Next, 10 g of the thus-obtained silicon-containing monomer, 10 g of toluene, 10 g of methyl isobutyl ketone, 1.0 g of potassium hydroxide and 5 g of water were poured into a 200 ml flask and stirred for one hour. Then, the solution was diluted with methyl isobutyl ketone and washed with 0.1 N hydrochloric acid until the pH dropped to not more than 8. The solution thus obtained was then filtered and stirred for 12 hours at 200 ° C, whereupon a polymer having a weight-average molecular weight of 5,000 was obtained. After cooling, 30 g of tetrahydrofuran was added and the resulting solution was stirred for one hour. This solution was then dropped into pure water, and the resulting precipitate was collected by filtration and dried in vacuo, to obtain 6.5 g of a white powder of a silsesquioxane polymer.

5 g of the polymer thus obtained, 10 g of tetrahydrofuran and 3 g of sodium hydroxide were poured into a 100 ml flask, and 3 g of 2-methyl-2-adamantylbromoacetate was gradually added in the form of drops. After stirring for one hour, the solution was precipitated in 100 g of pure water to give a solid polymer. The resulting polymer was dissolved in methanol and purified using an ion exchange resin. The resulting solution was then dropped into pure water, and the resulting precipitate was collected by filtration and dried in vacuo to obtain 4 g of a white powder of the desired silsesquioxane resin (polymer (x)). The structural formula of this resin is shown in [Formula 30]. The polydispersity of the polymer (x) was 1.14. Further, the relative proportions of the various structural units [i]: [ii] = 80:20 (molar ratio).

[Formula 29]

[Formula 30]

example 1

4 g of the polymer (x) obtained in Production Example 1 was dissolved in 75.9 g of ethyl lactate, and 0.12 g of triphenylsulfonium nonaflate and 0.008 g of tri-n-pentylamine were then added to form a positive resist composition.

Next, a lower resist film was formed using a solution as a lower resist material obtained by dissolving a novolak resin obtained by a condensation of m-cresol, p-cresol and formalin in the presence of an oxalic acid. Catalyst was produced in an organic solvent. This solution was made using a rotating disk ("Spinner") was applied to the surface of a silicon substrate and was then subjected to baking at 250 ° C for 90 seconds, whereby a lower resist layer having a film thickness of 300 nm was prepared.

The positive resist composition obtained above was then coated on the surface of the lower resist layer using a rotating disk, and was then prebaked and dried at 90 ° C for 90 seconds, thereby obtaining an upper resist layer having a film thickness of 100 nm and the formation of a resist laminate was completed.

Subsequently, this upper resist layer was selectively irradiated with an ArF excimer laser (193 nm) through a binary mask pattern, using an ArF irradiation apparatus NSR-S302 (manufactured by Nikon Corporation (NA (numerical aperture) = 0.60). σ = 0.75) was used.

A PEB treatment was then carried out at 90 ° C for 90 seconds and the resist layer was then developed for 60 seconds at 23 ° C in a 2.38 wt% aqueous solution of tetramethylammonium hydroxide to give a 120 nm line-and-tube. Space (L & S) pattern (I) with a favorable squareness was obtained.

This L & S pattern (I) was then subjected to dry etching with oxygen plasma using a high vacuum RIE apparatus (manufactured by Tokyo Ohka Kogyo Co., Ltd.), thereby forming an L & S pattern in the lower resist layer (US Pat. II) was formed.

The resulting L & S pattern (II) had dimensions of 120 nm and showed excellent squareness.

As a degas test, the above positive resist composition was applied to a silicon wafer having a film thickness of 2.0 μm, thereby forming a resist film. Subsequently, this resist film was subjected to 1,000-shot irradiation at 1000 mJ / cm ² using 193 nm wavelength light and an irradiation apparatus equipped with a gas collecting tube has been. Any gas generated was transported to the collection tube by means of a stream of nitrogen. Analysis of the collected gas using GC-MS revealed no detection of organic gases based on silicon. Further, organic, non-silicon based gases formed either during the cleavage of the acid-cleavable, dissolution-inhibiting groups or from the resist solvent were determined in an amount of about 150 ng.

Further, the light transmittance of the polymer (x) obtained in Production Example 1 was measured in the manner described below. The polymer (x) was dissolved in an organic solvent and then coated on the surface of a magnesium fluoride wafer in an amount sufficient to produce a film thickness of 0.1 μm in a dry state. This coated film was dried to form a resin film, and the transparency (absorption coefficient) to light having a wavelength of 193 nm and light having a wavelength of 157 nm was measured by using a vacuum ultraviolet spectrophotometer (manufactured by Jasco Corporation) ,

The results showed a value of 3.003 abs / μm for 157 nm light and a value of 0.0879 abs / μm for 193 nm light.

Production Example 2

With the exception of the replacement of 2-methyl-2-adamantyl bromoacetate in Preparation 1 with 2-ethyl-2-adamantyl bromoacetate, the same method was used as in Preparation Example 1 to prepare a polymer (x1) in which the 2-methyl-2 -adamantyl group of polymer (x) from Preparation Example 1 has been replaced by a 2-ethyl-2-adamantyl group.

Example 2

With the exception of replacing polymer (x) obtained in Production Example 1 with the polymer (x1) obtained in Preparation Example 2, a positive resist composition was prepared in the same manner as in Example 1. A resist laminate was then formed in the same manner as Example 1. When a resist pattern was formed in the same manner as in Example 1, a 120 nm line-and-space (L & S) pattern (I) with favorable squareness was obtained and the same method was then used to form a 120 nm line-and-space in the lower resist layer (" line and space ") (L & S) pattern (II).

Production Example 3

With the exception of replacing 20.0 g of hexafluoroisopropanol norbornene with 12 g of perfluoroisopentanol norbornene, the same method was used as in Preparation Example 1 to prepare a white, transparent polymer (x2) having the structural formula shown in [Formula 31].

[Formula 31]

Example 3

With the exception of replacing polymer (x) obtained in Production Example 1 with the polymer (x2) obtained in Production Example 3, a positive resist composition was prepared in the same manner as in Example 1. A resist laminate was then formed in the same manner as in Example 1. When a resist pattern was formed in the same manner as in Example 1, a 120 nm line and space (L & S) pattern (I) with favorable perpendicularity was obtained and the same method then became is used to form a 120 nm line-and-space (L & S) pattern (II) in the lower resist layer.

Comparative Example 1

Except for the replacement of polymer (x) of Example 1 with a polymer having the structural formula shown in [Formula 32] (the polymer of Preparation Example 3 in which the acid-cleavable, dissolution-inhibiting group of a 2-methyl 2-adamantyl group was changed to a 1-ethoxyethyl group), a resist pattern was formed in the same manner as in Example 1.

As a result, the upper resist layer could only be resolved down to 140 nm. In addition, when degas test measurements were made in the same manner as in Example 1, organic, non-silicon based gases were generated either during the cleavage of the acid-cleavable, dissolution-inhibiting groups or from the resist. Solvents were detected in an amount of about 600 mg.

[Formula 32]

Comparative Example 2

With the exception that the positive resist composition of Example 1 was replaced by a resist composition consisting of a solution of poly [p-hydroxybenzylsilsesquioxane-co-p-methoxybenzylsilsesquioxane-co-p (1-naphthoquinone-2-diazide] 4-sulfonyloxy) -benzylsilsesquioxane] in propylene glycol monomethyl ether, as described in Example 4 of the Japanese Unexamined Patent Application, First Publication No. Hei 06-202338 (or EP 0599762 ), a resist pattern was formed in the same manner as in Example 1.

As a result, the L & S pattern (I) formed in the upper resist layer had a round shape with a poor squareness and the limiting resolution was 180 nm.

In addition, the dimensions of the L & S pattern (I) and the L & S pattern (II) formed in the lower resist layer were different. The pattern could not be transferred to the lower resist.

Example 4

A component (A), a component (B), an organic solvent component and a quencher component described below were mixed together and dissolved to obtain a positive resist composition.

As the component (A), a mixed resin containing 85 parts by weight of the polymer (x) obtained in Production Example 1 and 15 parts by weight of a methacrylate-acrylate copolymer containing the three structural units shown in [Formula 33] was used. The proportions p, q and r of each of the structural units in the copolymer were p = 50 mol%, q = 30 mol% and r = 20 mol%, and the weight-average molecular weight was 10,000.

[Formula 33]

As component (B), 3 parts by weight of triphenylsulfonium nonafluorobutanesulfonate were used.

As the organic solvent component, 1900 parts by weight of a mixed solvent of propylene glycol monomethyl ether acetate and ethyl lactate (weight ratio 6: 4) was used.

The quencher component used was 0.25 parts by weight triethanolamine.

Next, using the thus obtained positive resist composition and using the same method as in Example 1 except that the prebake temperature was changed to 100 ° C and the film thickness of the upper resist layer was set to 150 nm, on the surface of a lower resist layer formed in the same manner as Example 1, an upper resist layer was formed, whereby a resist laminate was obtained.

The formation of the resist pattern was then performed in the same manner as in Example 1 except that the mask was changed from a binary mask to a half-tone mask and the temperature for baking after irradiation at 90 ° C, but additional postbake of the developed resist pattern was added for 60 seconds at 100 ° C.

The resulting resist pattern with a 1: 1 line and space pattern of 120 nm was inspected using a scanning electron microscope (SEM) to give a pattern having a favorable squareness , Furthermore, the sensitivity (Eth) was 28.61 mJ / cm ² . In addition, the bandwidth for the irradiation in which the 120 nm line pattern could be obtained with a ± 10% variation was a very advantageous 10.05%. The depth of field with which a 120 nm line-and-space pattern was obtained at a ratio of 1 1 was satisfactory 0.6 μm. In addition, the limiting resolution was 110 nm.

Example 5 (immersion lithography)

With the exception of changing the amount of triethanolamine to 0.38 part by weight, a positive resist composition was prepared in the same manner as in Example 4.

Next, using the thus obtained positive resist composition and using the same method as in Example 1 except that the temperature of the prebake was changed to 110 ° C and the film thickness of the upper resist layer was set to 150 nm On the surface of the lower resist layer formed in the same manner as in Example 1, an upper resist layer was formed, whereby a resist laminate was formed.

The resist laminate was then selectively irradiated with an ArF excimer laser (193 nm) through a phase shift mask pattern, using an irradiation apparatus NSR-S302B (manufactured by Nikon Corporation (NA (Numerical Aperture) = Then, immersion lithography treatment was performed by rotating the silicon wafer including the irradiated resist layer while dropping pure water continuously onto the surface at 23 ° C for a period of 5 minutes ,

A PEB treatment was then carried out at 90 ° C for 90 seconds, and the resist layer was then developed for 60 seconds in an alkaline developer solution at 23 ° C. As the alkali developer solution, a 2.38 wt.% Aqueous solution of tetramethylammonium hydroxide was used.

The resulting resist pattern with a 1: 1 line and space pattern of 130 nm was inspected using a scanning electron microscope (SEM) and the sensitivity at that point (Eth) became also determined.

In the positive resist composition of this example, Eth was 17.0 mJ / cm ² . This value is X2. The resist pattern showed an advantageous shape without superficial roughness.

On the other hand, the resulting Eth value was 18.0 mJ / cm ² when the positive resist composition of this example was used to form a resist pattern using conventional irradiation in air (normal irradiation) without the immersion lithography treatment described above was carried out. This value is X1.

The determination of the absolute value from the formula [(X2 / X1) -1] x 100 gave a value of 5.56. When the ratio of the sensitivity of the immersion lithography treatment relative to the sensitivity in the normal exposure was determined, the result was (17.0 / 18.0) or 0.94. In addition, the resist pattern had a favorable shape with no visible roughness of the surface.

Production Example 4

20.0 g of hexafluoroisopropanolnorbornene, 0.02 g of a 20% by weight solution of chloroplatinic acid in isopropanol and 30 g of tetrahydrofuran were poured into a 200 ml flask and the mixture was heated to 70 ° C. with stirring. 9.2 g of tetrachlorosilane was then added dropwise to the solution over a period of 15 minutes. After further stirring for 5 hours, the mixture was distilled to give 15 g of hexafluoroisopropanol norbornyltrichlorosilane (an Si-containing monomer represented by [Formula 29]).

Next, 10 g of the thus-obtained Si-containing monomer, 1.36 g of methyltrimethoxysilane (an Si-containing monomer represented by the chemical formula [34] shown below), 10 g of toluene, 10 g of methyl isobutyl ketone, 1 , 0 g of potassium hydroxide and 5 g of water poured into a 200 ml flask and stirred for one hour. The solution was then diluted with methyl isobutyl ketone and washed with 0.1 N hydrochloric acid until the pH dropped to not more than 8. The solution thus obtained was then filtered and stirred for 12 hours at 200 ° C, whereby a polymer having a weight-average molecular weight of 7,700 was obtained. After cooling, 30 g of tetrahydrofuran was added and the resulting solution was stirred for one hour. This solution was then dropped into pure water, and the resulting precipitate was collected by filtration and dried in vacuo to obtain 8 g of a white powder of a silsesquioxane polymer.

[Formula 34]

5 g of the polymer thus obtained, 10 g of tetrahydrofuran and 3 g of sodium hydroxide were poured into a 100 ml flask, and 3 g of 2-methyl-2-adamantylbromoacetate was gradually added dropwise thereto. After stirring for one hour, the solution was precipitated in 100 g of pure water to give a solid polymer. The resulting polymer was dissolved in methanol and purified using an ion exchange resin. The resulting solution was then dropped into pure water, and the resulting precipitate was collected by filtration and dried in vacuo to obtain 4 g of a white powder of the desired silsesquioxane resin (polymer (x3)). The structural formula of this resin is shown in [Formula 35]. The polydispersity of polymer (x3) was 1.93. In addition, the relative proportions of the different structural units [i]: [ii]: [iii] = 60:10:30 (molar ratio).

[Formula 35]

Example 6

A component (A), a component (B), an organic solvent component, an amine component that acted as a quencher, and an organic carboxylic acid component, which also acted as a quencher, were mixed together and dissolved, with a Positive resist composition was obtained.

As the component (A), a mixed resin containing 85 parts by weight of polymer (x3) obtained in Production Example 4 and 15 parts by weight of a methacrylate-acrylate copolymer containing the three functional units shown in [Formula 36] , used. The proportions s, t and u of each of these structural units in the copolymer were s = 40 mol%, t = 40 mol% and u = 20 mol%, and the weight-average molecular weight was 10,000.

[Formula 36]

As component (B), 2.4 parts by weight of triphenylsulfonium nonafluorobutanesulfonate were used.

As the organic solvent component, 1900 parts by weight of a mixed solvent of ethyl lactate and γ-butyrolactone (weight ratio 8: 2) were used.

As the amine component which acted as quenchers, 0.27 parts by weight of triethanolamine was used.

As the organic carboxylic acid component which acted as a quencher, 0.26 parts by weight of salicylic acid was used.

Subsequently, an organic composition AR-19 (manufactured by Shipley Co., Ltd.) for a reflection-reducing film was applied to the surface of a silicon wafer using a rotating disk. It was then baked and dried at 215 ° C for 60 seconds on a hotplate, forming a reflection-reducing film having a film thickness of 82 nm. The positive resist composition described above was then applied to the surface of this anti-reflection film using a rotating disk and was pre-baked and dried on a hot plate at 95 ° C for 60 seconds, thereby forming a resist layer on the surface of the anti-reflection film Film thickness of 150 nm was formed.

Next, this layer was selectively illuminated through a phase shift mask with an ArF excimer laser (193 nm) using an exposure apparatus NSR-S302B (manufactured by Nikon Corporation (NA (numerical aperture) = 0.60, 2/3 annular irradiation) A PEB treatment was then carried out at 90 ° C for 60 seconds, and the resist layer was then treated for 60 seconds in an alkali developer solution at 23 ° C. As the alkali developer solution, a 2.38 Wt .-% - used aqueous solution of tetramethylammonium hydroxide.

The resulting resist pattern with a 1: 1 line and space pattern of 130 nm was examined by using a scanning electron microscope (SEM), a pattern having an advantageous perpendicularity was found. In addition, the sensitivity (Eth) was 24.0 mJ / cm ² . In addition, the irradiation bandwidth over which the 130 nm line pattern could be obtained with ± 10% variation was a very advantageous 13.31%. The depth of field with which a 130 nm line-and-space pattern with a ratio of 1: 1 could be obtained was satisfactory 0.6 μm. In addition, the limiting resolution was 110 nm.

Example 7 (immersion lithography)

Using the positive resist composition prepared in Example 6, immersion lithography treatment was performed.

First, an organic composition for forming a reflection-reducing film named AR-19 (manufactured by Shipley Co., Ltd.) was applied to the surface of a silicon wafer using a rotating disk and then baked and dried at 215 ° C for 60 seconds on a hotplate, forming a reflection-reducing film layer having a film thickness of 82 nm. The positive resist composition was then applied to the surface of this antireflective film using a rotating disk and then prebaked and dried on a hotplate at 95 ° C for 60 seconds to form a resist on the surface of the antireflective film Layer was formed with a film thickness of 150 nm.

Next, this layer was exposed through a halftone phase shift mask with an ArF excimer laser (193 nm) using an exposure apparatus NSR-S302B (manufactured by Nikon Corporation (NA (numerical aperture) = 0.60, 2/3 annular illumination). Then, by rotating the silicon wafer including the exposed resist layer, simulated immersion lithography treatment was performed at 2000 rpm for 5 seconds and then at 500 rpm for 115 seconds, while pure water was added during a period of 2 minutes 23 ° C was dropped on the surface.

A PEB treatment was then carried out at 90 ° C for 60 seconds, and the resist layer was then developed for 60 seconds in an alkaline developer solution at 23 ° C. As the alkali developer solution, a 2.38 wt.% Aqueous solution of tetramethylammonium hydroxide was used.

The resulting resist pattern with a 1: 1 line and space pattern of 130 nm was measured using a scanning electron microscope (SEM) and the sensitivity at that location (Eop ) was also determined.

For the positive resist composition of this example, the Eop was 25.0 mJ / cm ² . This value is X2.

Furthermore, the resist pattern was of an advantageous shape with no apparent roughness of the surface or swelling.

On the other hand, the value of Eop was 24.0 mJ / cm ² when the positive resist composition of this example was formed to form a resist pattern using a normal exposure lithography method in which the aforementioned simulated immersion lithography treatment was not performed when, in other words, the formation of the resist pattern was carried out using the same method as described above, except that the simulated immersion lithography treatment was not performed. This value is X1.

The determination of the absolute value based on the formula [(X2 / X1) -1] x 100 gave a value of 4.16. When the ratio of the sensitivity of the simulated immersion lithography treatment relative to the sensitivity of the normal exposure was determined, the result was (25.0 / 24.0) or 1.04. In addition, the pattern profile had an advantageous shape with no visible surface roughness or swelling. Furthermore, the exposure bandwidth over which the 130 nm line pattern could be obtained with ± 10% variation was a very advantageous 12.97%. The limiting resolution was 110 nm.

Example 8 (immersion lithography)

A component (A), a component (B), an organic solvent component, an amine component acting as a quencher, and an organic carboxylic acid component also functioning as a quencher were mixed and dissolved together to give a positive resist Composition was obtained.

As the component (A), a mixed resin containing 85 parts by weight of the polymer (x3) obtained in Preparation Example 4 and 15 parts by weight of a methacrylate-acrylate copolymer containing the three structural units shown in [Formula 37] was used. The proportions v, w and x of each of these structural units in the copolymer were v = 40 mol%, w = 40 mol% and x = 20 mol%, and the weight-average molecular weight was 10,000.

[Formula 37]

As component (B), 2.4 parts by weight of triphenylsulfonium nonafluorobutanesulfonate were used.

As the organic solvent component, 1150 parts by weight of a mixed solvent of ethyl lactate and γ-butyrolactone (weight ratio 8: 2) were used.

As the amine component which acted as a quencher, 0.27 parts by weight of triethanolamine was used.

As the organic carboxylic acid component which acted as a quencher, 0.26 parts by weight of salicylic acid was used.

Subsequently, using a spinner, an organic composition AR-19 (manufactured by Shipley Co., Ltd.) for a reflection-reducing film was coated on the surface of the silicon wafer and was then baked and dried at 215 ° C on a hot plate for 60 seconds, thereby forming a reflection-reducing film having a film thickness of 82 nm. The positive resist composition described above was then applied to the surface of this antireflection film using a rotating disk and was pre-baked and dried on a hotplate at 95 ° C for 90 seconds, thereby forming a resist film having a film thickness of 150 nm was obtained on the surface of the reflection-reducing film.

Next, a mixed resin containing Demnum S-10 (manufactured by Daikin Industries, Ltd.) and Cytop (manufactured by Asahi Glass Co., Ltd.) (weight ratio in the mixture = 1: 5) was dissolved in perfluorotributylamine To form a material for a protective film based on fluorine with a resin concentration of 2.5% by weight. This material was applied on the surface of the above resist film using a rotating disk, and was then heated at 90 ° C for 60 seconds, thereby obtaining a protective film having a film thickness of 37 nm.

Then, as an evaluation test, 2 immersion lithography was carried out using a test equipment manufactured by Nikon Corporation, by conducting a test using a prism, water and the interference of two rays at 193 nm (a double-beam interference test). The same method is disclosed in the aforementioned Non-Patent Document 2, and this method is widely known as a simple method for obtaining a laboratory-scale L & S pattern.

In the immersion lithography of this Example 8, a layer of water solvent was formed between the upper surface of the protective film and the lower surface of the prism as the immersion solvent.

The exposure dose was selected to allow stable formation of an L & S pattern. Next, a PEB treatment was performed at 90 ° C for 90 seconds, and the protective film was then removed using perfluoro (2-butyltetrahydrofuran). Subsequently, development was carried out in the same manner as in Example 1 to obtain a 65 nm line-and-space pattern (1: 1). The shape of the pattern showed a high degree of squareness.

From the results of Examples 1 to 3 and Comparative Examples 1 and 2, it follows that in the two-layer resist method described above, when using a positive resist composition containing a silsesquioxane resin of the present invention, the degassing phenomenon ("degas phenomenon ") and a resist pattern having dimensions of about 100 nm can be formed with a high aspect ratio and an advantageous shape even when a high-energy light of not more than 200 nm or an electron beam is used as the exposure source. In addition, the positive resist composition has a high degree of transparency with respect to high-energy light of not more than 200 nm and electron beams, and provides excellent resolution.

In addition, it can be seen from the results of Example 4 that by using a positive resist composition containing a mixed resin of a silsesquioxane resin of the present invention and a (meth) acrylate ester resin, a resist pattern having dimensions of about 100 nm was formed can be, which shows a high aspect ratio and a favorable shape and also has an excellent margin and depth of field.

In addition, it can be seen from the results of Example 6 that even when using a positive resist composition containing a mixed resin of a silsesquioxane resin of the present invention and a (meth) acrylate ester resin, as a single layer, a resist pattern Dimensions of about 100 nm can still be obtained with a favorable shape and an excellent bandwidth for the exposure and depth of field.

In addition, it is apparent from the immersion lithography results of Examples 5, 7 and 8 that a positive resist composition used in the present invention is also ideal for immersion methods using a water solvent. In other words, an advantageous resist pattern can be generated without superficial roughness, and the sensitivity ratio indicates that the sensitivity is substantially the same as that at normal exposure, which means that the resist composition is resistant to any deteriorating effects of immersion. Solvent is. When a resist is deteriorated by the water solvent, superficial roughness appears within the resist pattern and the sensitivity varies by 10% or more.

Effects of the invention

As described above, with a silsesquioxane resin, a positive resist composition to be used in the present invention containing the silsesquioxane resin, a resist laminate using the positive resist composition, and a method of forming a resist pattern by using the Resist laminate, the degassing phenomenon can be suppressed and a resist pattern with high levels of transparency and resolution can be formed. In addition, according to the present invention, a use of a positive resist composition can be obtained by a method of forming a resist pattern which is ideal for immersion lithography processes.

Industrial applicability

The present invention can be used to form resist patterns and is extremely useful industrially.

Claims (3)

The use of a positive resist composition for forming a resist pattern by a method comprising an immersion lithography step, wherein when X1 denotes sensitivity, when a 1: 1 line-and-space resist pattern of 130 nm is formed in a normal exposure lithography method using a light source having a wavelength of 193 nm, and X2 denotes the sensitivity when obtaining an identical 1: 1 line-and-space resist pattern of 130 nm by a simulated immersion lithography method in which a step of bringing a solvent for said immersion lithography into contact between the step of selective irradiation and a step of baking after irradiation of a normal exposure lithography method using a light source having a wavelength of 193 nm is as stated Positive resist composition is a positive resist composition, i ie, as the resin component, a silsesquioxane resin for which an absolute value of [(X 2 / X 1) - 1] × 100 is not more than 8.0. The use according to claim 1, wherein during said immersion lithography step, an area between a resist layer composed of said positive resist composition and a lens at the lowermost position of an irradiation apparatus is filled with a solvent having a refractive index larger than the refractive index of air has. The use according to claim 1, wherein said silsesquioxane resin is a silsesquioxane resin comprising structural units represented by general formulas [1] and [2] shown below:

wherein R ¹ and R ² each independently represent a straight, branched or cyclic saturated aliphatic hydrocarbon group, R ^{3 represents} an acid dissociable, dissolution inhibiting group selected from the group consisting of the formulas [9 ] to [13] shown:

R ^{4 represents} a hydrogen atom or a straight, branched or cyclic alkyl group, each X group independently represents an alkyl group having 1 to 8 carbon atoms in which at least one hydrogen atom has been replaced by a fluorine atom, and m is an integer of 1 to 3 represents.